Coenobitoideans

Coenobitoideans, commonly known as hermit crabs, are a superfamily of decapod crustaceans. Unlike true crabs, which have a fully developed abdomen and tail tucked beneath their thorax, hermit crabs possess a soft, asymmetrical abdomen that is vulnerable to predation. To protect this soft posterior, they seek out and inhabit empty gastropod shells, such as those from snails, which they carry with them as they move.

These remarkable crustaceans are found in various marine environments worldwide, from shallow coastal waters to the deep sea. Some species are entirely marine, while others, like the well-known terrestrial hermit crabs, have adapted to life on land, though they still require access to moisture and often return to the sea to breed. Their diet is typically omnivorous, consisting of a wide range of food sources including algae, detritus, and small invertebrates.

The life cycle of coenobitoideans involves larval stages that are planktonic before settling and finding their first shell. As the hermit crab grows, it must shed its exoskeleton and find a larger shell to accommodate its increasing size. This process of shell exchange is a critical aspect of their survival and behavior, leading to complex social interactions and sometimes competition for suitable empty shells. Their unique adaptation to using discarded shells has made them a fascinating subject of study in evolutionary biology and ecology.